In popular culture, cyanides are said to be highly toxic. But there are many cyanides that really are, but many others that are not. Prussian blue, a cyanide compound, is given as a treatment to poisoning with Thallium and Caesium, for example.

The poisons referred to are usually hydrogen cyanide (HCN), and the chemicals which are similar to it, like potassium cyanide (KCN), and sodium cyanide (NaCN). (Such substances are called derivatives of hydrogen cyanide). Organic compounds that contain the CN group are called nitriles. Many of them are not as toxic. Some of them are even used to produce drugs.

Some people think that glucose (sugars) may be an antidote against cyanide poisoning. They think that sugar can bind the free cyano group, whereby some of the poison could be neutralized.